EXTERNAL CHARACTERS AND HABITS
of horizontal grooves over the interphalangeal joints, and transverse grooves on the palm. On the palm the papillary ridges stream in three directions from the wrist. Some pass to the inner border, others run to the
FIG. 2QA.—The foot of the Boruean Gibbon (A) and Orang-Outan (B) showing the flexure grooves and papillary ridges.
outer border, and an intermediate series passes straight down to the roots of the middle and ring fingers. At the proximal ends of the clefts between the fingers there are*groups of ridges forming concentric circles. The digits have oblique lines, and the apical pads have